1. Field
Embodiments of the present invention relate to a switching device comprising an optional power factor improvement converter, a DC-DC converter, a synchronizing rectifier circuit, and an alternating current driver circuit, and a method of controlling the switching device.
2. Description of the Related Art
Conventionally, as a switching power supply device comprising a power factor improvement converter and a DC-DC converter, there has been proposed a power supply device in which a switching power supply device is configured by combining a power factor correction (PFC) power supply section for switching a pulse current obtained by rectifying an alternating current (AC) power supply with a DC-DC power supply section for switching a direct current obtained by rectifying and smoothing the alternating current power supply so as to control a switching element of each of the power supply sections to be driven by one servo loop; and pulse width modulating means is provided to differentiate a pulse width of a drive pulse of a first switching element for switching the PFC power supply section and a pulse width of a drive pulse of a second switching element for switching the DC-DC power supply section from each other, thereby achieving high efficiency, downsizing, and restriction of generation of a harmonic current (refer to Jpn. Pat. Appln. KOKAI Publication No. 2002-101660, for example).
However, in a conventional switching power supply device as described in Jpn. Pat. Appln. KOKAI Publication No. 2002-101660, a smoothing capacitor for use in rectification has a high capacitance and a large current flows through the smoothing capacitor. In addition, the ripple voltage and ripple current of the smoothing capacitor are large, and thus, the smoothing capacitor is designed with a large capacitance. This large capacitance accounts for approximately 20% of the entire power supply device cost.